The present invention relates to controlling power supplied to a radiant heating element in a cooktop and more particularly to controlling power supplied to the radiant heating element such a glass-ceramic cooktop rapidly heats to a desired temperature.
Electronically controlled cooktops includes various user controls that are operated by a user to adjust the amount of heat and, ultimately, the temperature desired for cooking. A radiant heating element used for heating the cooktop can be powered by electricity, natural gas or other sources. Typically, the radiant heating element and the user controls are connected to a controller that controls the amount of heat supplied to the cooktop. The electronically controlled cooktop also includes temperature and other sensor that are connected to the controller to aid in controlling the heat supplied by the radiant heating source. The temperature and other sensors can also be used in conjunction with the controller to detect certain conditions that can arise during operation of the cooktop.
The user controls can include a user power selection device wherein the user can select a power level from, for example, a plurality of power levels. The user selected power level is supplied to a radiant heating element that heats the cooktop to a predetermined temperature that corresponds to the user selected power level. Typically, the user selected power level is provided to the radiant heating element at a constant, non-varying power level. This constant application of the user selected power level requires a predetermined amount of time before the radiant heating element heats the cooktop to the predetermined temperature corresponding to the user selected power level. Using this application of power at all user selected power levels, the predetermined time required to heat the cooktop can be high causing the user to become frustrated during the cooking process. Therefore, there is a desire to quickly heat the cooktop and to reduce the predetermined time required for heating such as to enhance the cooking experience for the user.
In addition, certain radiant heating elements, such as for example, electric coil-type elements, desire to have an oxide coating produced on the radiant heating element to increase the operational properties of the radiant heating element. Operating the radiant heating element at a high power level for a short period of time can typically, produce such an oxide coating. In addition, since the oxide layer can breakdown over time, the radiant heating element should be periodically operated at the high power level to maintain the oxide coating. Therefore, there is a desire to periodically operate the radiant heating element at a high power level for a short period of time to produce and maintain an oxide layer on the radiant heating element. In addition, there is a further desire to enhance the user""s cooking experience while also periodically operating the radiant heating element at a high power level.
In one exemplary embodiment, an apparatus for rapidly heating a cooktop is provided. The apparatus comprises a radiant heating element this is positioned below the cooktop. A controller is connected to the radiant heating element. The controller comprises a first switching device that is connected to the radiant heating element. A fast heat-up circuit is connected to the first switching device. The fast heat-up circuit comprises a proportional-plus-integral (PI) controller connected to the first switching device. The fast heat-up circuit also comprises a minimum selector having a minimum selector output. The minimum selector is connected to the PI controller, and the minimum selector output is connected to the first switching device. In addition, the fast heat-up circuit also comprises an anti-wind up controller that is connected to the PI controller and the minimum selector output. The controller further comprises a second switching device that is connected to the PI controller, and a look-up table that is connected to the second switching. The look-up table comprises a plurality of user power levels. Each of the plurality of user power levels is correlated to a respective user-selected temperature. The apparatus further comprises a user power input device that is connected to the controller and that allows selection of at least a first of the plurality of user power levels. The first user power level corresponds to a first respective user-selected temperature in the look-up table. Additionally, the apparatus comprises a temperature sensor that is connected to the controller to measure a temperature of the cooktop.
In another exemplary embodiment, a method for rapidly heating a cooktop is provided. The method comprises the steps of selecting a user power level using a user input device. The user power level corresponding to a respective user-selected temperature. A temperature of the cooktop is measured using a temperature sensor. The measured temperature is compared to the respective user-selected temperature. The respective user-selected temperature is supplied to a proportional-plus-integral (PI) controller when the measured temperature is less than about the respective user-selected temperature. The PI controller is connected to the radiant heating element when the measured temperature is less than about the respective user-selected temperature. A predetermined maximum temperature is supplied to the PI controller when the measured temperature is greater than about the respective user-selected temperature. A fast heat-up circuit is connected to the radiant heating element when the measured temperature is greater than about the respective user-selected temperature. A predetermined maximum temperature is supplied to the PI controller when the measured temperature is substantially equal to about the respective user-selected temperature. A fast heat-up circuit is connected to the radiant heating element when the measured temperature is substantially equal to about the respective user-selected temperature.